A pop is an undesirable audio artifact introduced in an audio system during power up. Generally, when an audio circuit is powered up there is a step in the supply and particularly to the reference voltage supplied to audio amplifiers. This discontinuity manifests itself as a pop sound which can be heard by the listener. Because a discontinuity is spectrally broad, it is especially undesirable.
Many techniques have been employed to address the pop problem. One method is to suppress the pop at the output, by suppressing any output while the audio system powers up. Another method is to isolate the most vulnerable portion of the audio system to pop from the output. Still others have employed charging a capacitor to generate a piecewise continuous reference voltage.